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machine424 merged 1 commit into from
May 9, 2025
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Enhancements to the prometheus high CPU FAQ page #79

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14 changes: 14 additions & 0 deletions content/Products/OpenshiftMonitoring/faq.md
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Expand Up @@ -91,6 +91,20 @@ Often, when "high" CPU usage or spikes are identified it can be a symptom of exp

A good place to start the investigation is the `/rules` endpoint of Prometheus and analyse any queries which might contribute to the problem by identifying excessive rule evaluation times.

A sorted list of rule evaluation times can be gathered with the following:

```bash
oc -n openshift-monitoring exec -c prometheus prometheus-k8s-0 -- curl -s 'http://localhost:9090/api/v1/rules' | jq -r '.data.groups[] | .rules[] | [.evaluationTime, .health, .name] | @tsv' | sort
```

An overview of the timeseries database can be retrieved with:

```bash
oc -n openshift-monitoring exec -c prometheus prometheus-k8s-0 -- curl -s 'http://localhost:9090/api/v1/status/tsdb' | jq
```

Within Prometheus, the `prometheus_rule_evaluation_duration_seconds` metric can be used to view evalutation time by quantile for each instance. Additionally, the `prometheus_rule_group_last_duration_seconds` can be used to determine the longest evaluating rulegroups.

## How do I retrieve CPU profiles?

In cases where excessive CPU usage is being reported, it might be useful to obtain [Pprof profiles](https://github.com/google/pprof/blob/02619b876842e0d0afb5e5580d3a374dad740edb/doc/README.md) from the Prometheus containers over a short time span.
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